The present invention relates to electroless plating of polyesters, in particular, to providing a surface uniformly receptive to metals which catalyze electroless deposition of nickel and copper.
The benefits of electroless plated, non-conductive articles, particularly plastic articles, are well known. In the finished product, the desirable characteristics of the plastic and the metal are combined to offer thereby the technical and aesthetic advantages of each.
Polymeric substrates are conventionally plated by preconditioning the surface by contact with an aqueous solution of at least one organic compound active for "conditioning" or "pre-etching" the surface of the plastic, etching with a strong oxidizing acid or base, seeding the surface with a noble metal catalyst, e.g., a palladium chloride solution, then immersing the seeded surface in an autocatalytic electroless plating solution where an initial coating of a conductive metal, e.g., copper or nickel, is established by chemical deposition. The metal deposit acts as a buss to allow a thicker coating of metal to be built up electrolytically.
In U.S. Pat. No. 3,567,594 there is disclosed a process of electroless plating which involves incorporating a siliceous filler into a plastic; molding the resulting plastic; conditioning the molded plastic product by treating the plastic product, in series, with an acid chromate etch followed by an HF treatment; preplating the conditioned article with an electrolessly plateable metal and electroplating the preplated article. The process was demonstrated using certain ethylene propylene copolymers and polypropylene. The process was represented as utile for polyesters. We evaluated the process on a "plateable" grade of a propylene polymer manufactured and sold by the assignee of the '594 patent, and found the treating procedures to be functional. When, however, applied to a mineral-filled polyester known as Valox.TM. 745, manufactured and sold by General Electric Company, the procedure failed.